Epoxy resins based on diglycidyl ether of bisphenol A were commercialized more than 50 years ago and their success is driven by the excellent adhesion, and high chemical and corrosion resistance that these coating provide when applied directly onto metal without a primer or other coatings. These high-performance epoxy primers were historically based on solvent based epoxy resins. Although these resins provide excellent performance, they have the disadvantage of relatively high volatile organic compounds (VOC) content.
Water-borne two component epoxy resin formulations can be an attractive alternative for the solvent-based systems despite their higher cost and, in some respects, slightly reduced performance. The application of aqueous epoxy resin dispersions has been known for about 30 years. For example, recently issued U.S. Pat. No. 9,938,428 B2 (incorporated herein by reference) describes aqueous epoxy resin dispersions which are low in VOC.